Grinding machine and method



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Jan. 12, 1937. J. EDGAR GRINDING MACHINE AND METHOD Original Filed July 9, 1 930 10 Sheets-Sheet 2 INVENTOR B570 71 7? Edgar W 6% M ATTORNEYS Maw Jan. 12, 1937.-

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Jan. 12, 1937. .J. EDGAR 2,067,177

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J. EDGAR GRINDING MACHINE AND METHOD Mai Original Fild July 9, 1950 10 Shets-Shet'? Mel afar Jan. 12, ED A GRINDING MACHINE AND METHOD Original Filed July 9, 1930 1O Sheets-Sheet 8 INVENTOR John Edgar ATTORNEYS Jan. 12, .1937. J EDGAR 2,067,177

GRINDING MACHINE AND METHOD Original Filed July 9, 1930 10 Sheets-Sheet 9 Fig. 26.

INVENTOR J 0777? Ed a?" BY ATTORN EYS Jan. 12,1937. E A I N 2,067,177

GRINDING MACHINE AND METHOD,

Original Filed July 9, 1930 10 Sheets-Sheet 10 l8? 2* I 5 274 mo m5 280 INVENTO John Edgar- ATTORN EYS Patented Jan. 12,1937

UNETED ST are John Edgar, Rockford, Ill., assignor to Barber- Colman Company, Rockford, 111., a corporation of Illinois Application July 9, 1930, Serial No. 466,764 Renewed December 12, 1935 33 Claims.

The present invention relates to improvements in grinding machines, and has particular reference to a new and improved machine for and method of grinding rotary thread milling cutters.

One of the objects of the present invention is to provide a novel grinding machine which will correctly form grind the teeth of rotary thread milling cutters having either straight, helical or inclined gashes, and being either cylindrical or tapered axially in form, the operation after the initial setting being fully automatic.

Another object resides in the provision of a new and improved grinding machine of the foregoing character which may be operated either automatically, semi-automatically or manually.

A further object is to provide a novel grinding machine for rotary thread milling cutters which is operable to take a series of light cuts successively along the blank until ground to the desired depth, thereby effecting an even distribution of heat and hence avoiding distortion and unevenness. 1

Another object resides in the provision of novel dressing means for the grinding element which after the initial setting is automatically adjusted to compensate for the progressive depth feed of the grinding element, and which more specifically is automatically effective upon manual repeated actuation after successive feeding movements of the grinding element toward the work to gradually change the cutting contour of the grinding element from a blunt form to a sharp V-shaped form, and to limit the abrasive action as to depth and form.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawings, Figure 1 is a fragmentary plan view of a machine embodying the features of my invention.

Fig. 2 is a fragmentary detail sectional view taken along line 2-2 of Fig. 4.

Fig. 3 is an enlarged plan View, partially in section, of the grinding wheel spindle head.

Fig. 4 is a fragmentary front elevational view of the machine.

Fig. 5 is a fragmentary detail view, partially sectioned along line 55 of Fig. 4.

Fig. 6 is a detail sectional view taken along line 6--6 of Fig. 5.

Fig. 7 is a fragmentary detail sectional view taken along line l-7 of Fig. 4.

Fig. 8 is a fragmentary rear elevational view of the machine.

Fig. 9 is a fragmentary sectional view taken along the line 9-9 of Fig. 1.

Fig. 10 is a. left end elevational view of the machine.

Fig. 11 is a right end elevational view of the machine.

Fig. 12 is a transverse vertical sectional view taken along line l2-l2 of Fig. 1.

Fig. 13 is a detail sectional View taken along line 3l3 of Fig. 12.

Fig. 14 is a fragmentary sectional view taken along line i l-l4 of Fig. 12.

Fig. 15 is a fragmentary sectional view taken along line 15-45 of Fig. 14.

Fig. 16 is a fragmentary horizontal sectional view of the left end of the machine through the headstock.

Fig. 17 is a fragmentary sectional view taken along line l'i-l'i of Fig. 16.

Fig. 18 is a sectional view taken along line l8-l8 of Fig. 16.

Fig. 19 is a fragmentary sectional View through the headstock of the machine taken along line Iii-49 of Fig. 16.

Fig. 20 is a fragmentary vertical sectional view taken along line 2il-20 of Fig. 16.

Fig. 21 is a fragmentary sectional View taken along line 2 l-2i of Fig. 16.

Fig. 22 is a fragmentary plan view illustrating the means at the rear of the machine for automatically actuating the power reversing control and also the primary clutches for the indexing mechanism.

Fig. 23 is a sectional view taken along line 23-23 of Fig. 24.

Fig. 24 is a fragmentary horizontal sectional View taken along line 24-24 of Fig. 8.

Fig. 25 is a fragmentary perspective view of the throw-out mechanism for the semi-automatic clutch in the indexing mechanism.

Fig. 26 is a fragmentary detail View of a portion of the mechanism shown in Fig. 25.

Fig. 27 is a fragmentary detailed view partially in section of the mechanism shown in Fig. 26.

Fig. 28 is a left side elevation of the wheel dressing mechanism.

Fig. 29 is a rear elevation of the wheel dressing mechanism.

Fig. 30 is a plan View partially in section of the wheel dressing mechanism.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to the drawings, the machine constituting the exemplary embodiment of the invention is adapted primarily for grinding thread milling cutters of the ring type. Cutters of this type comprise a plurality of radially relieved, substantially V-shaped teeth which are arranged in parallel peripheral rows alternating with annular grooves and which are separated by longitudinal flutes or gashes. The gashes may be either parallel or inclined in either direction to the cutter axis. In the present instance, I have shown a thread milling cutter A with righthand inclined gashes.

The grinding element preferably comprises an abrasive disk wheel B, the periphery of which is adapted to grind the annular cutter grooves and thereby form the cutter teeth, and the cutting contour of which is V-shaped in form when taking the final depth cut.

ln the grinding operation, the cutter blank A is rotated slowly, and the grinding wheel B is driven at a relatively high speed. At the start of the operation, the blank and the wheel are relatively adjusted laterally of the blank to efiect a light initial cut and longitudinally of the blank to grind the first groove on one end. A relative reciprocation between the blank and the wheel transversely of the blank is imparted once for each tooth and in timed relation to the rotation of the blank to provide the proper relief. When the blank has been rotated sufficiently to present all of the teeth in the initial row to the wheel, i. e. through one complete revolution where the teeth are ground consecutively, the cutter and the blank are separated, and during the next complete revolution of the blank, are indexed into position to grind the next annular groove.

When grinding a blank with inclined gashes, the

idle rotation of the blank is adjusted during each indexing step to compensate for the lead of the gashes. In the present instance involving righthand gashes, a slight additional degree of rotation is imparted to the blank.

The foregoing operation is repeated until all of the rows of teeth have been ground with an initial out, i. e. until the entire length of the blank has been traversed by the grinding wheel in a step-by-step grinding stroke. Thereupon, the blank and the grinding wheel are separated, and the latter is returned in a relative free continuous indexing stroke at a high speed to its initial position, and is given a relative incremental feed toward the blank preparatory to taking the second cut. Successive cuts along the blank are taken until the teeth are ground to the desired depth.

One feature of the invention resides in changing the form of the cut progressively with successive grinding strokes along the blank from a blunt contour to the final V-shaped contour. This is accomplished by automatically effecting an incremental feed of a suitable dressing tool toward the grinding wheel once for each incremental feed of the latter toward the blank so that in repeated truing of the grinding wheel its cutting contour will be changed in accordance with the desired change in the tooth form as the grinding progresses todepth.

A relative compensatory adjustment of the grinding wheel laterally of the blank in timed relation to the indexing movement and the quick return is available for grinding tapered cutters.

Work support and, drive The machine comprises a suitable elongated horizontal bed or frame 3| formed on the top with longitudinal guides 32 on which a work carriage 33 is mounted for translation. The right end of the carriage 33 is formed on the top with longitudinal guides 34 on which a suitable tailstock 35 is mounted for adjustment. On the left end of the carriage 33 and preferably integral therewith is a headstock 36 formed with a tubular bearing 31. A cutter spindle 38 is rotatably journaled in the bearing 31 for endwise movement with the carriage 33, and has an arbor section 39 on which the cutter blank A is removably mounted. The free end of the arbor section 39 is supported by the tailstock 35.

The power inlet comprises a cone pulley 40 which is secured to a short drive shaft 4i journaled at the upper left front corner of the frame 3!, and which is adapted to be connected by a belt 42 to an external countershaft (not shown) adapted to be connected through a reversible clutch (not shown) to a suitable source of power. A drive pinion 43 on the shaft 4| meshes with a large drive gear 44 rotatably mounted on a hollow shaft 45 into which the left end of the spindle 38 is splined for relative axial movement.

The gear 54 has a hub 45 projecting from both sides, and is formed in its right face with an annular concentric cavity 4'1. An adjusting disk 48 is mounted for rotary adjustment on the gear hub 56 within the cavity 4'5, and is formed with an annular T-slot 49 opening to the face of the gear 44. A plurality of bolts 50 carried by the gear 54 and with their heads in the slot 49 serve as means for securing the disk 48 in position of adjustment to the gear. This adjustment permits setting the gashes of the work in proper relation to the grinding wheel B.

A pair of diametrically opposed studs 5| are mounted on the disk 48 and project from the outer face thereof. Ro-tatably mounted on each of the studs 5| is a pair of gears 52 and 53 of which the outer gear 52 is the smaller. The outer gears 52 mesh with a terminal gear 54 formed on a sleeve 55 journaled on the shaft 45, and normally held in fixed position, and the inner gears 53 mesh with a terminal gear 56 keyed to the shaft 45. It will thus be evident that the gear 44 is the driving element of a planetary gear transmission for slowly rotating the work spindle 38.

Indexing mechanism The relative step-by-step indexing movement and the free-return movement of the grinding wheel B along the blank A are obtained by driving the slide or carriage 33 in timed relation to the rotation of the blank. The drive means for this purpose (see Figs. 1 and 16) derives its power from the gear 44 through a gear 51 keyed to the hub 45. The gear 5! is connected through an idler gear 58 to a gear 59 keyed to a shaft 50 extending along and journaled on the rear of the frame 3!.

Secured to the hub of the gear 59 is a gear Si in mesh with a gear 52 rotatable on a sleeve 63 in turn rotatable on a fixed stub shaft 64. A suitable clutch 55 comprising a single clutch tooth on the hub of the gear 52 and a similar opposed clutch tooth on one end of a clutch sleeve 66 axially splined to the sleeve 63 is provided for connecting and disconnecting the gear 62 and the sleeve 53. The clutch B5 is always closed during the full automatic operation of the machine.

An annular collar Bl is keyed to the sleeve 63, and extends partially into a central recess 68 formed in the hub of a mutilated gear 99 rotatably mounted on the shaft 69. The collar 61 is formed in its periphery with a notch 19 (see Fig. 20) normally engaged by a spring-pressed pawl l'l pivotally mounted in the hub of the gear 69, and is effective through the pawl to drive the gear in a counter-clockwise direction as viewed in Fig. 20, but not in the reverse direction.

The toothed sector of the gear 99 is movable once during each rotation into mesh with a gear l2 rotatable on a stub shaft 13 in axial alinernent with the shaft 69, and is adapted to rotate the gear through one complete revolution during each engagement. The stub shaft "i3 is suitably journ-aled on the frame 3i and in the adjacent end of the shaft fill.

Secured to and concentric with the gear 69 is a circular disk it (see Fig. 3.7) which is notched at 15 in the region of the gear sector to receive the periphery of a disk l6 secured to and concentric with the gear l2 so as to permit rotation of the latter when in mesh with the sector, and which is adapted to engage in an arcuate notch il in the periphery of the E9 to lock the latter against rotation when the gear sector is out of mesh with the gear '52. The construction thus constitutes a modified form of Geneva motion device.

As an additional means for locking the gear 12 in fixed position when out of mesh with the mutilated gear (it, the disk iii is formed in its periphery with a notch 58 slightly tapered inwardly. A plunger 19 slidably disposed in a vertical guide 86 (see Fig. 20) on the frame 3i is formed on its upper end with a tooth 8i adapted to enter the notch l8 and thereby accurately locate and lock the gear "it in position. and on its lower end with a gear rack 82. A gear sector 83 secured to a stub shaft 8 5 meshes with the rack 92, and is urged upwardly by a coil spring 85. Also secured to the shaft 84 is a cam arm 36, the free end of which projects into the path of a cam block 9! secured to the right face of the gear 69. The cam block 87 is located to depress the follower arm 86 and thereby withdraw the tooth 8! from the disk it just before the gear (59 moves into mesh with the gear 12, and to release the arm and thereby restore the tooth into engagement with the disk so that the tooth will snap into the notch Tl when the gear if has made one complete revolution.

Axially splined on the shaft 13 between the gears 59 and i2 is a clutch sleeve 88. One end of the sleeve 38 is formed with a single tooth adapted to be moved into coacting engagement with a similar opposed tooth on the hub of the gear i2, the teeth constituting a clutch 89 for connecting the latter to the shaft 13. The other end of the sleeve 86 and the hub of the gear 59 are formed with the opposed elements of a clutch 99 movable into engagement to connect the gear 59 to the shaft 33.

The outer end. of the shaft '13 is connected through speed-change gears Si, 92 and 93 (see Figs. 9 and 10) to a shaft es journaled in the left end of the frame 3 l. A screw shaft 95 is journaled at its ends in the inner end of the shaft 9 3 and the right end of the frame 3i, and is formed with a feed screw 95 in threaded engagement with a fixed nut 97 in 2. depending lug 96 on the underside of the carriage 33. Back-lash between the feed screw 98 and the nut 91 is taken up by a weight 99 (see Fig. 8) connected to the right end of the carriage 33 through a cord,l leading over a pulley iii! in a bracket #92 on the right end of the frame 3 l.

A clutch its comprising opposed clutch elements on the inner end of the shaft' 94 and the adjacent end of a clutch sleeve #96 splined for axial movement on the shaft is provided for connecting the two shafts. A shifting yoke Hi5 engages the sleeve 5&3 and is secured to a rock shaft W5 extending to the front of the frame 31 and there provided with a suitable hand lever 48?. The clutch M33 is closed during full automatic or semi-automatic operation of the machine, and is opened for manual operation.

It will be evident that when the clutch 89 is closed, the indexing drive will be connected from the gear 59 through the Geneva motion device to the shaft l3 and thence to the feed screw 96 to index the cutter A in a step-by-step grinding stroke to the right to effect a relative movement of the grinding wheel 13 to the left. The gearing is such that each indexing movement is just sufficient to move the succeeding peripheral groove ice-tween the teeth into operative registry with the grinding wheel.

Upon opening the clutch 89 and closing the opposed clutch 99, the gear 59 will be connected directly to the shaft '53 and thence to the feed screw 9%, thus constituting a continuous rapid drive. Under the last condition, the rotation of the gear must be reversed to move the cutter A in a quick-return stroke to the left into its initial position for the next depth out. However. upon such reversal, the collar will be ineffective to rotate the mutilated gear 69. and hence the Geneva motion device will remain idle.

lvieans is provided for reversing the clutch sleeve 88 to alternately close the clutches 89 and 9?] respectively at the end of the grinding stroke to the right and the quick-return stroke to the left, and for simultaneously reversing the rotation of the gear 59 from which both drives are taken. This means (see Figs. 22, 23, and 24) preferably comprises a fluid operated engine 1538 having a cylinder 89 mounted on the rear of the frame 3|. the cylinder is, and is connected to a piston rod I H projecting at both ends through the cylinder heads.

The left end of the piston rod H! (as viewed from the front of the machine) EXJEl'ldS slidably through an eye H2 (see Figs. 8 and 20) on the lower end of a lever H9 pivoted at its upper end. Two coil springs H4 are disposed on the rod ill with their adjacent ends in abutting engagement with opposite sides of the eye i i2 and with their remote end in abutting engagement with spaced stop collars H5. The lever 553 is formed intermediate its ends with a bifurcated portion which carries a shifting ring H5 in engagement with the clutch sleeve 93.

The right end of the rod ill is formed with a yoke ill which engages a roller H8 mounted on the free end of a lever H9 secured to a vertical shaft H9. The upper end of the shaft I29 is connected to suitable actuating means (not 4 shown) for the reversing clutch (not shown) in the countershaft (not shown) adapted for connection through the belt 42 with the cone pulley 59.

The cylinder :09 is formed with suitable pas- A piston H9 is slidably disposed in 7 its lower end in communication with the inlet line I26, and opening to the periphery through a radial port I29 movable into registration with either of the ports I23 and H4. The exterior of the plug I21 is formed with a peripheral space I3llterminating adjacent opposite sides of the port I28, and communicating through a radial [bore I3I with an axial bore I32 exhausting to the atmosphere.

Secured to the upper end of the valve plug I21 isa bell crank lever I33 (see Figs. 16 and 22) A coil tension spring I34, anchored to the frame, isconneeted to one arm of the lever I33 and tends to swing'this arm against a fixed stop pin I35. The other arm of the lever I33 constitutes a pawl E35 adapted to be swung against the action of the spring I34 into interlocking engagement with the notched end of a latch I31. A lever arm I33 is pivotal with the latch I31, and is connected at its free end to a coiled tension spring I39 anchored to the frame 3| and serving to hold the latch against the pawl I36 at all times.

The pawl I33 when seated in the latch I31 defines one position of the plug in which the port 829 registers with the port I23 to direct pressure fluid to the right end of the cylinder, and in which the space I30 communicates with the port I24 to vent the pressure fluid in the left end of the cylinder to the atmosphere. The resultant movement of the piston H8 to the left serves to close the clutch t8 and to change the rotation of the work spindle '33 and the gear 58 so that the blank A will be rotated in a counter-clockwise direction as viewed in l2, and the timed step-by-step indexing movement to the right will be instituted.

A trip dog i mounted on the carriage 33 for movement therewith has an inclined surface adapted to ride against a pin I4I extending upwardly from the free end of the lever arm I38, and to gradually swing the latter rearwardly until at the end of the indexing movement, the latch I31 releases the pawl I36. Thereupon, the lever I33 is moved under the influence of the spring 134 into engagement with the stop pin I35. The latter defines the other position of the valve plug E21 in which a port I29 registers with the port I24 to direct pressure fluid to the left end of the cylinder, and in which the space I30 communicates with the port I23 to vent the pressure fluid in the right end of the cylinder to the atmosphere. The resultant movement of the piston Iiil to the right serves to close the clutch 90 and to change the rotation of the work spindle 33 and the gear 59 so that the blank A will be rotated in clockwise direction as fluid in Fig. 12 and a quick-return movement to the left will be instituted.

' A reversing dog I42 mounted on the carriage 33 for movement therewith is positioned to engage the free 'end of the lever I33 at the end of the quick-return movement, and to move the same against the action of the spring I35 into position for engagement by the tooth of the latch I31, thereupon reinstituting the step-by-step indexing movement preparatory to taking a new segm t Q h r When the blank A is formed with inclined gashes, the work spindle 38 is angularly adjusted proportionately with each step in the indexing movement so as to compensate for the inclination of the gashes. This adjustment may be positive or negative depending on whether the blank A has right-hand or left-hand gashes. In the present instance, the blank A is shown with righthand gashes, and hence is turned through one complete revolution plus the additional compensatory rotation during each increment in the indexing movement. The means for this purpose (see Figs. 4, 7, and 16) comprises a gear I43 formed on the sleeve 55 which supports the terminal gear 54 of the planetary spindle drive. The gear I43 is connected through an idler gear I44 to a gear rack I45 formed on the lower end of a bar I46 vertically reciprocable in a guideway I41.

The upper end of the bar I46 carries a pivotal block I48 which is slidably disposed in a longitudinal guide-way I49 formed in a horizontal bar 256. The bar i513 is pivoted adjacent one end as indicated at IN, to a horizontal bar I52 of which one end is rigidly secured to an upstanding bracket l53, mounted on the work carriage 33 for movement therewith, and of which the other end is slidably disposed in a horizontal guide I54 formed on the upper end of an upstanding bracket I55 on the machine frame. The free end of the pivotal bar I50 constitutes a pointer movable along an arcuate scale I56 formed transversely on the horizontal bar I52, and carries a clamp bolt ilil adjustable in an arcuate slot I58 extending along the scale. When the pivotal bar I!) is secured in a horizontal position at the zero point on the scale I56, no movement will be imparted to the rack I45 upon translation of the carriage 33 either direction, and hence the terminal gear 53 will be stationary. However, if the pivotal bar I56 is adjusted above or below the zero point of the scale I56 at an angle corresponding to that of the cutter gashes, translation of the carriage 33 will impart a reciprocatory movement to the rack I45, thereby effecting a compensatory drive ire-ugh the terminal gear 54 as aforesaid.

The periodic indexing for the carriage 33 is subject at will to manual control so as to facilitate properly locating the grinding wheel B relative to the tooth grooves of the blank in setting up the machine, and to permit rough grinding. The means for this purpose (see Figs. 16, 18 and 25 to 2'7) comprises a shoe B59 engaging a peripheral groove 265 in the clutch sleeve 65, and secured to the lower end of a lever I6I pivotally mounted intermediate its ends as at I62 on a bracket I63. The upper end of the lever I6I is connected to a shifter rod I54 (see Figs. 1 and 8) extending along the rear of the machine and slidably supported in bracket arm I65 on the machine frame 3|. A suitable handle I66 is secured to the free end of the rod I64 which is capable of actuation to close the clutch 65 and institute the indexing operation.

The clutch 65 is opened automatically upon indexing the blank A the distance between two tooth grooves. To this end, an L-shaped bracket I61 is secured to the right face of the gear 62. A star wheel I58 is rotatably mounted on a stud I69 secured to the outwardly extending arm of the bracket I61, and consists of a triangular prism with a similar triangular prism superimposed on the inner end, thus providing three equi-angular points at the outer end and six equian'gular points at the inner end. A springpressed detent I70 mounted in the base of the bracket I 61 is formed in its outer end with a V-shaped notch adapted to engage any one of the six points of the star wheel I68.

Pivotally mounted on a bracket I?! in the machine frame 3| is a pawl I72, the heel of which is pressed by a spring I13 against a stop pin I'M. The pawl II2 projects into the path of the six points of the star wheel I68, and constitutes a fixed abutment for indexing the star wheel through one-sixth of a revolution once for each revolution of the gear 62. A pawl I 75 pivotally mounted on the lower end of the lever I6I and with its heel pressed by a spring I16 into engagement with a stop pin II'I projects into the path of the triangular portion of the star wheel I68, and is adapted for engagement by one of the three points through two indexing movements of the star wheel once for every two revolutions of the gear 62 to automatically open the clutch 65. The pawl I 75 is mounted on the lever I6I only when the operation is to be semi-automatic, and is removed for full automatic operation. It will be evident that in semi-automatic operation, the clutch 65 is closed manually to institute each indexing movement, and that it will be opened automatically when the blank A has been indexed exactly one groove.

Grinding wheel support The grinding wheel B is mounted on one end of a drive spindle I'I8 (see Fig. 3) which is rotatably mounted in a spindle head I79 slidably adjustable on ways I80 formed on the end of a suitable bracket support It. An adjusting screw I82 rotatably anchored on the bracket I8I is in threaded engagement with the spindle head I19. Secured to the spindle I78 within the head I19 is a pinion I83 which is connected through an idler gear I84 to a gear I85, both gears I84 and I85 being mounted on the side of the bracket I8I. A sheave I86 is rigid with the gear I85, and is adapted to be connected through a belt I8'I to a suitable source of power (not shown).

The bracket MI is mounted between two spaced upstanding supports I88 and I89 (see Figs. 28 and 30) for pivotal adjustment about a horizontal shaft I90 extending perpendicularly to the blank axis, and is adapted to be secured to the support I88 by means of a locating pin I9I and a bolt I92 in either of two horizontal positions at opposite sides of the shaft I90, thus locating the grinding wheel B in position to engage the blank A in a horizontal axial plane.

The supports I88 and I89 are formed on a horizontal feed slide 93 (see Figs. 11 and 12) mounted for adjustment transversely of the blank A along ways I94 on a horizontal supporting slide I95. A feed screw I 96 in threaded engagement with a nut I 97 on the underside of the slide I93 is journaled in a bearing bracket I98 on the front end of the slide I95. The outer end of the feed screw I96 (see Figs. 5 and 12) is provided with an enlarged head I99 rotatable in a seat 200 formed in the front face of the bracket I98. A cylindrical block 20I is notched at its inner end to interfit with an annular peripheral end flange 202 formed on the outer end of the head I99, and is rigidly secured to the latter by means of bolts 288. The flange 292 is somewhat larger in diameter than the block ZllI, and hence defines an outwardly facing peripheral shoulder 264 about the latter. A cam abutment 205 is seated in a recess in the front end of the block 20! and projects forwardly therefrom.

Extending slidably through alined axial bores 206, 261, and 208 in the screw I96, the block 20I and the abutment 205 is an elongated draw bolt 209, the rear end of which is in fixed threaded engagement with a lug 2I0 on the supporting slide I95 and the front end of which is formed with a bearing ring or eye 2II. A bifurcated rotary cam 2!?! provided with a hand lever 2I3 is pivotally mounted on opposite ends of a pin 2I4 extending through the eye 2II in bearing engagement with the cam abutment 205, and serves as means for anchoring the feed screw I96 rigidly to the slide I95. A coiled compression spring 2I5 is disposed on the draw bolt 209 within an enlargement 2I6 of the inner end of the bore 206 in end abutment with the inner end of the enlargement and the front of the lug 2I0, and serves upon releasing the cam 2I2 to shift the feed screw I96 forwardly in the bearing I98, and thereby retract the grinding wheel B from the blank A into inoperative position.

A relative automatic feed increment toward the blank A is imparted to the grinding wheel B once for each longitudinal cut. The means for this purpose (see Figs. 1, 2, 4, 5, and 6) comprises a gear 2II formed on the front end of the block 20!, and disposed in a circular recess 2I8 formed centrally in the front face of a large gear 2I9 freely rotatable on the block 20I. Journaled in and extending through the web of the gear 2I9 at diametrically opposed points are two stub shafts 220 and 22I. A pair of gears 222 and 223 are secured respectively to the front ends of the shafts 220 and 22I in mesh with the gear 2, and are suitably disposed in circular recesses 224 and 225 formed in the front face of the gear 2I9. Likewise, a pair of gears 226 and 221 are secured respectively to the rear ends of the shafts 220 and 22I within suitable circular recesses 228 and 229 formed in the rear face of the gear 2I9.

The gears 226 and 221 mesh through idler gears 230 and 23I with a gear 232 which is disposed in a central circular recess 233 formed in the rear face of the gear 2I9, and which is secured to the front face of a gear 234 rotatably mounted on the block 29I and abutting against the flange shoulder 204. Thus, the parts are held in assembled relation between the shoulder 204 and the gear 2I'I. Normally, the gear 234 is held against rotation in position of adjustment by means of a spring-pressed lock pin 235 mounted in a side bracket 236 on the slide I95 for engagement between the gear teeth. It will be evident that the gear 2I9 constitutes the driving element of a planetary gear transmission for the feed screw I96 of which the gear 232 is the fixed terminal gear, and the gear 2I'I is the outlet terminal gear. The gear 2I9 meshes with a worm 23'! on a vertical shaft 238 journaled in the bracket 236, and is provided with a suitable hand wheel 239 on its upper end.

The lower end of the shaft 238 is provided with a ratchet 240 and supports a pivotal pawl arm 24I (see Fig. 2) directly over the latter. A pawl 242 is pivotally mounted on the underside of the arm 24! for engagement with the ratchet 240, and is movable at will into inoperative position against a stop 243. A bent leaf spring 244 anchored on a pin 245 on the arm 24I has one end in engagement with the stop 243 and the other end is flexed engagement with the heel of the pawl 242, and serves to hold the pawl yieldingly in either extreme position.

The free end of the arm 24I is connected through a rod 246 to one arm'of a bell-crank lever 241 pivotallymounted on the slide I95. The other arm of the lever 241 carries an adjustable stop screw 248 adapted to engage the slide I95 to define the starting point of the working stroke of the pawl 242, and is disposed in the path of a dog 249 on the work carriage 33 for engagement thereby at the end of the free-return stroke. A coiled tension spring 250 secured at its ends to the lever MI and an anchor pin 25I on the slide I 95 tends to hold the screw248 against the slide.

Suitable means is available for imparting a transverse movement to the grinding wheel B in timed relation to the indexing movement of the blank A when grinding taper work. This means (see Figs. 1, 4, and 9) preferably comprises a spiral gear 252 on the feed screw shaft 95 and meshing with a spiral gear 253 on a transverse shaft 254 extending to the front of the frame EN. The front end of the shaft 254 is squared for the reception of a suitable hand lever (not shown), and supports a pivotal change gear bracket 255. A gear 256 on the shaft 254 meshes with a change gear 251 adjustable on the bracket 255 and movable into engagement with the gear 234. When the gears 234 and 251 are brought into mesh, the lock pin 235 is withheld from the gear 234, and the feed screw I96 for the slide I93 will be actuated in timed relation to the feed screw 96 for the carriage 33.

Dressing mechanism Means is provided for dressing the grinding wheel B from time to time to maintain the desired form and to remove glaze from the grinding surface. This means (see Figs. 28, 29, and 30) is mounted on and includes the shaft I rotatably adjustable in the supports I88 and I89. A positioning disk 258 is keyed to the front end of the shaft I90 and is adjustably disposed in a recess 259 formed in the rear side of the support I88. Clamp bolts 260 with their heads disposed in an annular T-slot 26I in the front face of the disk 258 are provided for securing the latter in position of adjustment to the support I88.

The rear end of the shaft I90 is formed with a bifurcated head 262 in which a leg 263 is sup ported for pivotal adjustment about a stud 264. A coiled compression spring 265 disposed in a bore 266 in the rear end of the shaft I90 abuts against the leg 263 below the stud 264 and serves to hold the leg yieldingly in a substantially vertical position. A triangularly-shaped head 261 is mounted on the upper end of the leg 263 and extends transversely thereof over the grinding wheel B. Extending through the head 261 is an operating shaft 268 with a gear 269 secured to the rear end in a circular recess 210, and a hand lever 21I secured to the front end.

Two relatively inclined guideways 212 and 213 are formed in the rear end of the head 261, and intersect each other at the angle subtended between the side faces of the grinding wheel B and also intersect opposite sides of the recess 210. Slidably disposed in the guideways 212 and 213 and held therein by an outer cover plate 214 are two gear racks 215 and 216 in mesh with the gear 269. The lower ends of the racks 215 and 216 are reduced in width and cross each other, and carry suitable dressing tools 211 and 218 for the oppositely inclined surfaces of the grinding Wheel 13. The racks 215 and 216 are so positioned relatively to each other that when one tool 218 is at its uppermost limit of travel, the other tool 211 is at its lowermost limit of travel, thus avoiding interference.

Provision is made for automatically feeding the dressing tools 211 and 218 toward the grinding wheel B in timed relation to the rearward incremental feed of the latter toward the blank A in the course of the grinding operation. To this end, the lower end of the leg 263 is disposed in the path of a stop screw 219 adjustably secured in the upper end of a vertical arm 288. The latter is formed on one end of a supporting bar 28I rigidly secured to one side of the slide I for adjustment longitudinally thereof. It will be evident that as the grinding wheel B is fed rearwardly to depth by the slide I93, the head 261 will be tilted rearwardly through coaction of the leg 263 with the relatively fixed screw 219, thus advancing the dressing tools 211 and 218 toward the grinding wheel. start of the grinding operation, the periphery of the wheel is blunt. As the grinding operation proceeds to full depth, the cutting contour of the wheel B becomes sharper and sharper upon repeated dressing until the final V-shaped form is reached.

Relieving mechanism Means is provided for effecting a relative relieving reciprocation between the blank A and the grinding wheel B transversely of the blank once for each tooth as. it passes through the grinding zone, and for separating the blank and the grinding wheel during each indexing movement and during the free-return stroke (see Figs. 8 and 12 to 15). To this end, the supporting or relieving slide I95 carrying the grinding wheel B is mounted for reciprocation on horizontal transverse ways 282 formed on the machine frame 3|. A heavy coiled compression spring 283 is interposed between an inner wall 284 of the frame 3I and an adjustable plug 285 in a depending lug 286 on the underside of the slide I95, and tends to urge the grinding wheel B away from the blank A.

Pivotally secured at its upper end to the rear end of the slide I95 is a depending cam lever 281 normally fulcrumed about its lower end. A cam follower block 288 is secured to the lever 281 intermediate its ends, and rides on a rotary relieving cam 289 having a spiral face a terminating in an abrupt drop b. The cam 289 is secured to a longitudinal shaft 290 journaled at its ends on the machine frame 3| and connected at its left end through a train of speed-change gears 29I, 292, 293, and 294 (see Fig. 10) to the main drive shaft M. The rotation of the cam 289 is so timed to the blank A that the grinding wheel B will be fed rearwardly during the grinding of each tooth so as to generate a suitable radial relief, and will then be returned quickly to initial position for the succeeding tooth.

The lower end of the lever 281 is fulorumed against a roller 295 mounted in the bifurcated front end of a plunger 296 slidably disposed in a bearing 291 on the rear of the machine frame 3I. The rear end of the plunger 296 rides on a rotary separating cam 298 having a peripheral dwell face 0 of substantially a peripheral dwell face d of smaller radius. also of approximately 180, an abrupt drop shoulder e and a gradual rise shoulder 1 connecting the ends of said dwell faces. Upon rotation of the cam 298 in a counter-clockwise direction as viewed in Fig. 12, movement of the drop shoulder e past the For the initial cut at the plunger 2% permits the spring 283 to withdraw the grinding wheel B quickly from the blank A into remote inoperative position, the lever 28? fulcruming about the cam follower 288. The grinding wheel B is retained in this position while the dwell face (1 rides past the plunger. The inclined rise shoulder f returns the grinding wheel B to operative position by fulcz'uming the lever 28! about the block 288, and the dwell face 0 retains the grinding wheel in this position.

The cam 2% is rotatably mounted in suitable anti-friction hearings on a fixed shaft 299 mounted in spaced brackets 390 and Sill on the rear of the frame 3!. A gear 302 (see Figs. 14 and 15) is rotatably mounted on the hub of the cam 28 i. and carries a pivotal pawl 30.? spring-pressed into engagement with a notch 304 in the periphery of the hub for rotation therewith in a clockwise direction as viewed in Fig. 15, The gear 362 meshes with a gear 385 on the right end of the shaft Bil which is suitably journaled in a bearing 33% on the bracket Thus, the cam 298 is driven in timed relation to the blank A during the grinding stroke. In the present instance, the cam 298 makes one complete revolution for two of the blank A, the cam faces 0 and 02 serving to locate the grinding wheel respectively in and out of cutting position during alternate revolutions of the blank. During the return stroke of the blank A, the cam 298 is idle, and is positioned with the cam face (if in engagement with the plunger 2% so as to hold the grinding wheel B out of engagement with the blank.

For manual operation, the cam 298 is locked in position with the cam face 0 in engagement with the plunger 22% to locate the grinding wheel B normally in cutting position. Preferably, the means for this purpose comprises a lock pin 30! slidably mounted in the bracket 38%! for movement into a hole 308 in the adjacent side face of the cam 298. Separation of the grinding wheel B from the blank A may be efiected when desired by means of the lever 2E3.

Resume of operation The machine may be adjusted for full automatic operation, semi-automatic operation or manual operation.

In the set-up of the machine for full automatic operation, the clutch 593 (Fig. 9) is closed; the bar I56 is adjusted to compensate for the inclination of the gashes on the blank A; the pawl H5 is removed from the lever It! so that the clutch 35 will remain closed; the lever 233 is adjusts to position the feed slide I93 in its rearward position for control by the cam 298; the pawl 2 52 (Fig. 2) is in engagement with the ratchet 2% to connect the automatic feed; the pin 38? is out of engagement with the cam 298; the work spindle 39 is adjusted into correct relation to the cams 289 and 298; and the grind ing wheel B is positioned at the proper depth to take an initial out along the first groove at the right end of the blank A. At the start, the grinding wheel B has a blunt contour. If the blank A is tapered longitudinally, the gear 251 is brought into engagement with the gear 23d and the pin 235 is retracted from the latter to connect the shaft 254 to the feed screw I96.

The power drive is now connected. There upon, the blank A is rotated in a counter-clockwise direction as viewed in Fig. 12, and the grinding wheel B is reciprocated by the cam 239 transversely cf the blank once for each tooth to provide the desired relief. After one complete revolution of the blank A, the grinding wheel B is retracted into inoperative position by ihe earn 298, and during the next revolution of the blank it is indexed to the right to position the next groove in registry with the grinding wheel. Aiter completion of the indexing movement, the grinding wheel B is returned into operative position through the action of the cam 293.

The foregoing operation is repeated until the blank A has b en indexed its full length. across the grinding wheel B for the initial cut. At this point, the pneumatic motor M38 is actuated to reverse the clutch (not shown) in the main power drive, and the clutch 85 9*? (see Fig. 16). As a result, the rotation of t e spindle E38 and the shaft 56 is reversed, and the inding senw is driven in the opposite direction. to return the blank A at a relatively high speed n a cor-thuous movement to its i. "ii position.

During this r: vement, the Geneva motion device in the normal sliep-bv-step indexing drive is inoperative, and the cam stationary, with the cam face d (Fig. in engagement with the plunger 298 to position the grinding wheel B out of engagement w th the blank A. At the end of the return movement, the grind ng wheel B is given automatic incremental feed toward the blank A for the next longitudinal cut, and the pneumatic engine 508 is actuated to establish the initial connections. The grinding wheel B now is dressed. The resulting contour is somewhat sharper ti n the initial contour since the dressing device is advanced toward the grinding wheel B in timed relation to the feed of the lat er toward the blank A.

The foregoing cycle of operations is repeated until the blank A is ground to the desired depth. At the end of the operation, contour of the grinding wheel will be the same as the desired contour of the teeth on the blank A. If the taper drive is connected, the wheel will be advanced toward blank A in timed relation to the step-by-step indexing movement to compensate for the angle of the taper on the blank.

The set-up for semi-automatic operation is the same excepting that the pawl H5 is mounted on the lever H3! (Fig. 25). In operation, the handle #36 is actuated to close the clutch F- o institute the indexing operation. and the H5 through coaction with the star wheel 488 is effective to open the clutch at the end of each indexing movement. Semi-ant:rnat cv operation p eces the indexing under manual control. In all other respects, the operation is the same as the ifull automatic operation. Manual control of the indexing is do 'rable when setting up the machine for full a cmatic on ton, and ticularly to facilitate correcth ositioning the grinding wheel B relative t0 the grooves between the teeth on the blank A.

In the set-up for manual operation. the air supply to the motor N18 is shut the clutch 63 in the drive for the indexing screw 96 is open; the pawl 1'55 in the operating me... ianism for the clutch 65 is removed; the pawl 12 i? (Fig. 2) moved into inoperative position to disconnect the automatic feed; the gear in the drive for the cam 258 is removed; and the cam 298 is locked in position by the pin Sill with the cam race in engagement with the plunger 256.

The power drive is connected to drive the spindle 33 and the relieving cam 289. The lever 2l3 is actuated to withdraw the grinding wheel B from the blank A to permit indexing and the free return move-ment. The blank A is traversed longitudinally by turning the shaft 254. The grinding wheel B is fed toward the blank A by turning the hand wheel 239. It will be evident that in the manual operation, the automatic feed for the grinding wheel B may be connected, and that other specific automatic features may be utilized.

I claim as my invention:-

1. A machine for form and relief grinding rotary cutters having generally longitudinally inclined gashes and a plurality of longitudinally spaced annular rows of teeth comprising, in combination, a rotary shaft for supporting the cutter blank, means including a differential mechanism for rotating said shaft, a slide mounted for rectilinear movement perpendicularly to said shaft, a grinding wheel mounted on said slide, means acting on said slide for automatically effecting a relieving reciprocation between said wheel and the blank once for each tooth being ground, means for automatically efiecting a relative step-by-step indexing movement between said wheel and the blank longitudinally of the latter and in timed relation to the rotation of the blank to present different rows of the teeth successively to said wheel, and means for automatically adjusting said differential mechanism during each step in said indexing movement to compensate for the inclination of said gashes.

2. A machine for form and relief grinding ro tary cutters having generally longitudinal gashes and a plurality of longitudinally spaced annular rows of teeth comprising. in combination, a rotary support for the cutter blank, means for rotating said support, a grinding wheel, and means for automatically effecting a relative stepby-step indexing movement between said wheel and the blank in one direction longitudinally of the blank and in timed relation to the rotation of the blank to present consecutive rows of the teeth successively to said wheel, and for automatically effecting a relative continuous return movement between said wheel and the blank in the other direction longitudinally of said blank at the end of said step-b-y-step movement, and means for automatically effecting a relative separation between said wheel and the blank once during each step of said indexing movement and during said return movement.

3. A machine for form and relief grinding rotary cutters having generally longitudinal gashes and a plurality of longitudinally spaced annular rows of teeth comprising, in combination, a rotary support for the cutter blank, means for rotating said support, a grinding wheel, and means for automatically effecting a relative reciprocatory movement between said wheel and the blank longitudinally of the blank and in timed relation to the rotation of the blank, said movement in one direction being intermittent to present consecutive rows of the teeth successively to said wheel and in the other direction serving to return said wheel and the blank to initial position, means for automatically effecting a relative separation between said wheel and the blank once during each step of said intermittent movement and during the return movement, and means for automatically eifecting a relative incremental feed of said wheel toward the blank once for each complete reciprocation.

4. A machine for form and relief grinding rotary cutters having generally longitudinal gashes and a plurality of longitudinally spaced annular rows of teeth comprising, in combination, a rotary support for the cutter blank, means for rotating said support, a grinding wheel, and means for continuously effecting an automatic relative reciprocatory movement between said wheel and the blank longitudinally of the blank and. in timed relation to the rotation of the blank, said movement in one direction being intermittent to present consecutive rows of the teeth successively to said wheel and in the other direction being uninterrupted and serving to return said wheel and the blank to initial position, means for effecting a relative 'separationbetween said wheel and the blank once during each step of said intermittent movement and during the return movement, and means for eifecting a relative incremental feed of said wheel toward the blank once for each complete reciprocation.

5. A machine for relief grinding a work blank having generally longitudinal gashes and a series of longitudinally spaced peripheral rows of teeth comprising, in combination, a grinding wheel, a rotary support for the blank, means for effecting a relative relieving reciprocation between said wheel and the blank laterally of the blank, means for effecting a relative step-by-step indexing movement between said wheel and the blank in one direction longitudinally of said blank, means for effecting relative free return indexing movement in the opposite direction between the wheel and the blank, and trip means automatically operable at the ends of said indexing movements to render said last two mentioned means alternately operable and inoperable.

6. A machine for grinding rotary cutters having generally longitudinal gashes and a plurality of longitudinally spaced annular grooves comprising, in combination, a reversible power drive, a rotary support for the cutter blank connected to said drive, a grinding wheel, means connected to said drive for automatically effecting a relative reciprocation between said wheel and the blank longitudinally of said blank, said means including a slow intermittently acting indexing mechanism, a high-speed return mechanism, and a two-way clutch for selectively rendering one or the other of said mechanisms operative, trip means automatically operable at each end of said reciprocation to reverse said drive and said clutch, means for automatically effecting a relative relieving reciprocation between said wheel and the blank during the periods between the intermittent indexing movements, and means for automatically effecting a separation between said wheel and the blank during each intermittent indexing movement and during the return movement.

7. A machine for grinding rotary cutters having generally longitudinal gashes and a plurality of longitudinally spaced annular grooves comprising, in combination, a reversible power drive, a rotary support for the cutter blank connected to said drive, a grinding wheel, means connected to said drive for automatically effecting a relative reciprocation between said wheel and the blank longitudinally of said blank, said means including a slow intermittently acting indexing mechanism, a high-speed return mechanism, and a two-way clutch for selectively rendering one or the other of said mechanisms operative, pneumatic trip means automatically operable at each end of said reciprocation to reverse said drive and said clutch, means connected to said drive for automatically effecting a relative relieving reciprocation between said wheel and the blank during the periods between the intermittent indexing movements, and means connected to said drive through a oneway clutch for automatically effecting a separation between said wheel and the blank once during each intermittent indexing movement and during the return movement.

8. A machine for grinding rotary cutters having generally longitudinal gashes and a plurality of longitudinally spaced annular grooves comprising, in combination, a power drive, a rotary sup port for the cutter blank, a grinding wheel, means connected to said drive for automatically effecting a relative reciprocation between said wheel and the blank longitudinally of said blank, said means including an intermittently acting indexing mechanism, a return mechanism, and a clutch for selectively rendering one or the other of said mechanisms operative, trip means automatically operable at each end of said reciprocation to reverse said clutch, and means for automatically efiecting a-relative relieving reciprocation between said wheel and the blank during the periods between the intermittent indexing movements, and means for automatically effectinga separation between said wheel and the blank during any relative longitudinal movement. a

9. In a grinding machine, in combination, a support, a slide on said support, a grinding wheel mounted on said slide, a dressing device mounted on said slide for pivotal movement generally in the plane of said wheel and having a dressing tool movable toward or from the periphery .of said wheel upon said pivotal movement, an arm on said device, and an adjustable stop on said support in engagement with said arm and operable to swing the latter in timed relation to the movement of said slide on said support.

10. In a grinding machine, in combination, a support, a slide on said support, a spindle on said slide, means including .a shaft for driving said slide, a cross slide on said support, .a feed screw for said cross slide journaled in said support, means including a differential mechanism for actuating said feed screw, said mechanism having a terminal gear, a gear rigid with said terminal gear,.spring detentmeans for releasably locking said last mentioned gear in fixed position, and means available at will for gearing said shaft to said last mentioned gear.

11. In a grinding machine, in combination, a base, a rotary spindle on said base, a .relieving slide on said base reciprocable transversely of said spindle, a relieving cam journaled in said base, a lever pivoted at one end to said slide and engaging intermediate its ends with said cam, a spring for urging said lever against said cam, a plunger reciprocable in said base, one end of said plunger constituting an abutment for the other end of said lever, a separating cam journaled on said base and engaging the other end of said plunger, and means for rotating said earns.

12. In a grinding machine, in combination, a base, a rotary spindle on said base, a relieving slide on said base reciprocable transversely of said spindle, a relieving cam journaled in said base, a lever pivoted .at its upper end to said slide and engaging intermediate its ends with said cam, a spring for urging said lever against said earn, a plunger slidable in said base, one end of said plunger constituting an abutment for the lower end of said lever, a separating cam engaging the other end of said plunger, means for driving said relieving cam in timed relation to said spindle, and means including a one-way clutch for turning said separating cam through one complete revolution for every two revolutions of said spindle.

13. In a grinding machine, in combination, a base, a relieving slide on said base, a relieving cam for reciprocating said slide, a feed slide on said relieving slide, a spindle journaled in said feed slide, a feed screw for said feed slide, said feed screw having a head rotatably and slidably mounted in said relieving slide, a draw bar extending through said screw and anchored to said relieving slide, a spring tending to move said head in one direction in said relieving slide, and a cam lever pivoted to said bar and available to move said screw in the other direction against the action of said spring.

14. The method of relief grinding a work blank having generally longitudinal gashes and a series of longitudinally spaced annular rows of teeth which comprises rotating the blank in one direction, effecting a relative relieving reciprocation between said wheel and the blank in timed relation to the rotation of said blank, eifecting a relative step-by-step indexing movement between said wheel and the blank in one direction longitudinally of said blank and once for each complete grinding revolution of the blank, separating said wheel from the blank at the end of said indexing movement, then effecting a relative continuous return indexing movement between said wheel and the blank in the opposite direction, and during said return movement effecting a relative feed of said wheel toward the blank for the next cut along the blank.

15. In a grinding machine, in combination, a base, a rotary spindle for a work blank, a support for said spindle movable on said base axially of said spindle, a slide mounted on said base for movement transversely of said spindle, means for moving said support, a rotary screw for feeding said slide, a planetary gear transmission connected to said screw, a power drive adapted to be connected at will to said transmission to feed said slide in timed relation to the movement of said support, and drive means connected to said transmission and operable in response to movement of said support into a predetermined position to impart an incremental feed to said screw.

16. A grinding machine for a rotary work blank having generally longitudinal gashes and a series of longitudinally spaced peripheral rows of teeth comprising, in combination, a base, a rotary support for the blank, a carriage for supporting said support and mounted on said base for reciprocatory movement axially of said blank, a rotary grinding wheel mounted on said base in operative relation to said blank, drive means for rotating said support, and drive means for reciprocating said carriage, said last mentioned drive means including a driving element rotatable in timed relation to the rotation of said support, a driven translating element operatively connected to said carriage, a Geneva motion device, a two-way clutch selectively adjustable to connect said driving element directly to said driven element or said motion device to said driven element, a clutch for connecting said driving element to said device, and means for automatically actuating said first mentioned clutch reversely from one position to the other respectively upon movement of said carriage into its opposite end positions.

17. A grinding machine for a rotary work blank having generally longitudinal gashes and a series of longitudinally spaced peripheral rows of teeth comprising, in combination, a base, a rotary support for the blank, a carriage for supporting said support and mounted on said base for reciprocatory movement axially of said blank, a rotary grinding wheel mounted on said base in operative relation to said blank, drive means for rotating said support, and reversible drive means for reciprocating said carriage, said last mentioned drive means including a driving element rotatable in timed relation to the rotation of said support, a driven translating element operatively connected to said carriage, a Geneva motion device, clutch means selectively operable to connect said driving element directly to said driven elementor said motion device to said driven element, means for connecting said driving element to said device, and means rendering said motion device effective in only one direction.

18. A grinding machine for a rotary work blank having generally longitudinal gashes and a series of longitudinally spaced peripheral rows of teeth comprising, in combination, a base, a rotary support for the blank, a carriage for supporting said support and mounted on said base for reciprocatory movement axially of said blank, a rotary grinding wheel mounted on said base in operative relation to said blank, drive means for rotating said support, and reversible drive means for reciprocating said carriage, said last mentioned drive means including a driving element rotatable in timed relation to the rotation of said support, a driven translating element operatively connected to said carriage, a Geneva motion device, clutch means selectively operable to connect said driving element directly to said driven element or said motion device to said driven element, means for connecting said driving element to said device, means rendering said motion device efiective in only one direction, means operable auto- 1 matically in response to movement of said carriage into either end position to reverse said drive means and to actuate said first mentioned clutch means to change the drive connection to said driven element, and means operable froni said driven member for automatically opening said last mentioned clutch means after each of a series of predetermined step-by-step movements of said carriage in one direction.

19. A grinding machine for a rotary work blank having generally longitudinal gashes and a series of longitudinally spaced peripheral rows of teeth comprising, in combination, a base, a rotary support for the blank, a carriage for supporting said support and mounted on said base for reciprocatory movement axially of said blank, a rotary grinding wheel mounted on said base in operative relation to said blank, drive means for rotating said support, and reversible drive means for .reciprocating said carriage, said last mentioned drive means including a driving element rotatable in timed relation to the rotation of said support, a driven translating element operatively connected to said carriage, a Geneva motion device, clutch means selectively operable to connect said driv ing element directly to said driven element or said motion device to said driven element, means for connecting said driving element to said device, means rendering said motion device effective in only one direction, and means operable automatically in response to movement of said carriage into either end position to reverse said drive means and to actuate said first mentioned clutch means to change the drive connection to said driven element.

20. A grinding machine for a rotary work blank having generally longitudinal gashes and a series of longitudinally spaced peripheral rows of teeth comprising, in combination, a base, a rotary support for the blank, a carriage for supporting said support and mounted on said base for reciprocatory movement axially of said blank, a rotary grinding wheel mounted on said base in operative relation to said blank, drive means for rotating said support, and reversible drive means for reciprocating said carriage, said last mentioned drive means including a driving element rotatable in timed relation to the rotation of said support, a driven translating element operatively connected to said carriage, a Geneva motion device, clutch means selectively operable to connect said driving element directly to said driven element or said motion device to said driven element, clutch means for connecting said driving element to said device, means rendering said motion device effective in only one direction, means operable automatically in response to movement of said carriage into either end position to reverse said drive means and to actuate said first men tioned clutch means to change the drive connection to said driven element, said last mentioned clutch means being adapted to be closed manually, and means adapted to be rendered inoperable at will and when in operable condition to be actuated in timed relation to said driving element to open said last mentioned clutch means after each of a series of predetermined step-by-step movements of said carriage effected by the drive through said motion device in one direction.

21. A grinding machine for a rotary work blank having generally longitudinal gashes and a series of longitudinally spaced peripheral rows of teeth comprising, in combination, a base, a rotary support for the blank, a carriage for supporting said support and mounted on said base for reciprocatory movement axially of said blank, a rotary grinding wheel mounted on said base in operative relation to said blank, drive means for rotating said support, and reversible drive means for reciprocating said carriage, said last mentioned drive means including a driving element rotatable in timed relation to the rotation of said support, a driven translating element operatively connectedto said carriage, a Geneva motion device,

atwo-way clutch selectively adjustable to connect said driving element directly to said driven element or said motion device to said driven element, a clutch for connecting said driving element to said device, means for automatically actuating said first mentioned clutch reversely from one position to the other respectively upon movement of said carriage into its opposite end positions, an actuator operable manually to close said last mentioned clutch, a gear driven from said driving element, a star wheel pivotally mounted eccentrically on said gear and movable into operative position for engagement with said actuator to open said last mentioned clutch, and abutment means on said base forindexing said star wheel into said position upon rotation of said gear through a predetermined degree.

22. A grinding machine for a rotary work blank having generally longitudinal gashes and a series of longitudinally spaced peripheral rows of teeth comprising, in combination, a base, a rotary support for the blank, a carriage for supporting said support and mounted on said base for reciprocatory movement axially of said blank, a rotary grinding wheel mounted on said base in operative relation to said blank, drive means for rotating said support, and reversible drive means for reciprocating said carriage, said'last mentioned drive 

